Part 1. The Field of the Invention
This invention relates to photography and more precisely, to photographic film packs or assemblies comprising a container holding self-developing film unit(s) integrated with an electrical power supply system.
Part 2. Description of the Prior Art
U.S. Pat. Nos. 3,705,542; 3,543,662; 3,543,663; 3,595,661 and commonly owned, copending U.S. Pat. application Ser. No. 399,321 filed Sept. 21, 1973 by S. M. Bloom, J. W. Foley and N. S. Hadzekyriakides and now U.S. Pat. No. 3,877,045 relate to photographic film packs comprising an enclosure containing selfdeveloping film units integrated with a power supply system. Such film packs are presently employed exclusively in a photographic camera sold by Polaroid Corporation of Cambridge Massachusetts, U.S.A. under the trade name "SX-70".
Essentially, film packs described in those Patents and Application comprise an opaque enclosure containing a dark slide for covering an exposure station in a forward wall of the container, a stack of individual "self-developing" film units positioned behind the dark slide, means for urging the stack of film units towards the forward wall to position the uppermost film unit in the stack in the exposure station and an electrical power supply system for operating electrical mechanisms of a camera designed for using the pack.
When the film pack is inserted into the camera, the dark slide is removed through a withdrawal slot at one end of the enclosure to uncover the exposure station and the uppermost film unit is urged into position in the exposure station by the means mentioned before which usually involves a spring biased platen.
After exposure, the uppermost film unit is advanced, from the exposure station through the withdrawal slot into engagement with cylindrical rollers and processing of the exposed film unit is initiated as the unit is advanced between the rollers.
"Self-developing film" of such packs is sometimes described as an integral negative-positive film unit having as essential elements, a photosensitive element having a photosensitive system for providing a diffusion transfer image pattern, an image-receiving element, an opacification system and a rupturable container holding a processing composition. The elements are integrated with the unit so that the processing composition can be distributed within the unit to install a diffusion transfer image pattern in the image-receiving element and the pattern is viewable against a reflective background without separation. The film units are adapted for processing outside the camera since effective protection against further exposure is provided by way of the opacification system which in some integral negative-positive film units is integrated with the unit prior to exposure of the photosensitive system while in others, the opacification system is integrated with the unit after exposure. In the preferred integral negative-positive film units, the opacification system comprises a combination of light-absorbing dyes and a light-reflecting material or pigment and this combination is included in the rupturable container and distributed between the photosensitive and image-receiving elements after exposure. Further details relating to the integral negative-positive film units may be found in U.S. Pat. Nos. 3,415,644; 3,415,645; 3,415,646 and 3,647,437 among others.
As mentioned, the film packs of the present invention also include an electrical energy power source contained within the enclosure. Essentially, the power source comprises a battery of the type described in detail in U.S. Pat. Nos. 3,543,662; 3,563,805; 3,617,387 and 3,734,780 among others. Such batteries are flat or planar primary batteries of the LeClanche type including a zinc anode system, a manganese dioxide cathode system and an aqueous electrolyte system generally comprising an aqueous ammonium chloride, zinc chloride and usually a small amount of mercuric chloride. When the film pack is inserted into the camera, the battery integrated therewith is connected to the camera's electrical system to provide the electrical energy sufficient to operate any circuits of the camera which can include an automatic exposure control circuit, a flash mode circuit, film transport circuits and processing mechanism circuit among others. The output of the battery is designed to continue to supply the requisite energy until all film units in the pack are exposed and transported from the camera. At that time, the pack--containing the integral battery--is discarded.
Photographic film packs having an enclosure containing film units integrated with an electrical energy power source represent an important factor in successfully presenting to the public the distinctive features and advantages of the advanced photographic system involving the camera and film units described before. For example, one distinctive advantage of the integration of the battery and the film units involves the positive assurance that the power supply is replenished concurrently with the renewal of the film supply. Further, the integration of the power supply with the film unit permits storage of both the film and battery in the same package prior to use and optimum storage conditions can be controlled and maintained. For example, each film pack is normally hermetically sealed within lighttight, moisture proof packages and these packages can be stored under conditions designed to assure maximum reliability for the performance characteristics desired of the film unit and battery. Equally important, the integration of film units and battery is accomplished in a fashion that does not impose inordinate design constraints on the final film pack but instead permits the use of primary batteries which are low in cost and not incompatable with the disposable feature of the pack. Also the integration can be accomplished at acceptably low production costs by way of efficient, high volume, on-line production techniques.
On occassional instances, the above-described film packs have been found deficient in fully providing the desired performance characteristics. This deficiency has been attributed to incomplete or inadequate sealing of the battery components and such deficiencies unfortunately can occasionally occur in any production process despite the use of highly sophisticated techniques and equipment and stringent quality control programs specifically designed to eliminate or minimize such occurrences. In any event, it is believed that the deficient sealing permits volatile material generated in the battery such as gaseous ammonia, mercury or water to contact the film units within the pack. In turn, such gaseous products are believed to be capable of adversely affecting the photographic film characteristics and properties such as the film speed and balance shifts.
Commonly owned, copending U.S. Pat. application Ser. No. 399,321 now U.S. Pat. No. 3,877,045 mentioned before is directed to a solution for the problem posed by the evolution of gaseous products from batteries integrated with film units. Essentially, the solution presented involves the integration of gas collection means in the pack to capture gaseous effluents from the battery. In a particularly preferred embodiment, a metal salt adapted to form an amoniate is dispersed in a gas absorbant having an active surface area. The present invention provides another solution for effectively protecting film units positioned in a container with an energy source from any adverse effects that could occur by contact of the units with any gaseous material that may evolve from the energy source.